Basic ARC 5 stone stock unmodified transmitter running on the MD-7 modulator/PS with a pair of good and not gassy 1625's.  When keyed, the tube 'lights up' orange inside the tube, looking like the filament went from orange to lightbulb like brightness, but, it is not the filament changing.  ARC 5 TX components have been checked for health.  Anybody see that one before?

Charlie, W4MEC in NC